Inflammatory Bowel Disease Flashcards
What is IBD
Inflammatory bowel disorder characterised by chronic and spontaneous relapsing of inflammation
Pathogenesis of IBD
Immune disease
Environmental factors (smoking, diet, hygiene, medical history)
Gut/microbial alterations
Genetic susceptibility
Microbiota
Group of microorganisms that reside in a previously established environment
Dysbiosis
An unhealthy change in the normal microbiota
Specialised epithelial cells
Goblet cells: Mucus, repair and inflammation modulatory factors
Paneth cells: Anti-microbial peptides
Mucosa innate immune function
- Pattern recognition receptors (NOD-like receptors) that mediate responses to microbiota
- Divert tolerance or inflammation pathways
Inflammatory processes
- Breakdown in mucosal barrier function so Lamina propria exposed to antigens
- Infiltration with immune cells (Neutrophils, macrophages, dendritic cells, natural killer cells, B and T cells)
- Local elevation of TNF α, IL-1 β, IFN γ
- Defective regulation of immunosuppression
- Activated T cells activate other inflammatory cells like macrophages and B cells recruiting more inflammatory cells
T effector cells
Ulcerative colitis has excess Th2 and Th17 cells
Chron’s disease has excess Th1 and Th17 cells
They both have defect in Tregs
Genetic susceptibility
- Defects in mucosal barrier
- Exposure to bacterial products
- MUC19, OCTN, DLG5 - Defects in bacterial sampling
- Pattern recognition receptors NOD2
- Bacterial peptidoglycan receptor
- LPS receptor - Defects in immune response
- IL23R defect
- IL-10 pathway
- INF γ gene
- Autophagy genes (ATG16L1)
Laboratory tests
Increased C-reactive protein ESR increased Platelet count increased Hameoglobin decreased Leukocytosis - Fecal calponectin IBD antibodies are pANCA (Antineutrophil cytoplasmic antibody) and ASCA (Antisaccharomyces cerevisiae antibody)
Positive pANCA and negative ASCA = UC
Negative pANCA and positive ASCA = CD
Clinical signs of Chron’s Disease
Abdominal pain Perianal disease Anorexia/Weight loss Bloody diarrhoea Growth failure
Occurs in any part of GIT and lesions discontinuous
Clinical signs of Ulcerative colitis
Bloody diarrhoea
Abdominal pain
Passage of mucus
Usually starts in rectum and spreads proximally in continuity
Macroscopic features
For Chron’s disease:
- Transmural inflammation
- Extends into the deeper layer of intestinal wall
- Bowell wall thickened and rigid
- Lumen narrowed
For Ulcerative colitis:
- Ulceration and inflammation of the inner lining of the colon and rectum
Th1, Th2 and Th17
Th1: IL-12, TNF α and IFN γ
Th2: IL-5, IL-13 and IFN γ, TNF α
Th17: IL-17 and IL-23
Chron’s and ulcerative colitis gene defects
Chron’s: MUC19, EP4 receptor (PTGER4), ATG16L1, PTPN2, card15, octn
Ulcerative colitis: IL-10 defects, INF γ, IL26 genes, PLA2G2E, CARD15, OCTN
Treatment options
- Antibiotics
- Anti-inflammatory
- Immunosupressants
- Biologicals
Anti-inflammatory
- Aminosalicylates (5-ASA
Activate PPARy
Inhibit eicosanoid synthesis
Inhibit production of proinflammatory cytokines
Inhibit adhesion molecule expression
Stimulate production of anti-inflammatory molecules
Modulates proliferation, differentiation and survival of immune cells
- Sulfasalazine, mesalazine, olsalazine, balsalazide - Glucocorticoids
Modify gene transcription
Inhibit production of proinflammatory cytokines
Inhibit synthesis of proinflammatory enzymes
- Budesonide, Prednisone
Immunosupressants
- Thiopurines i.e. Azathioprine, 6-mercaptopurin
Inhibit T cell and B cell proliferation - Methotrexate
Inhibit production of proinflammatory mediators - Cyclosporin
Inhibit synthesis of IL-2 and IL-2R, inhibiting clonal expansion of T cells
Anti-TNF agents
Adalimumab, infliximab and golimumab
- Inhibits proinflammatory cytokine release i.e. IL-1, IL-6
- Inactivates leukocyte
- Induces inflammatory cells apoptosis
Infliximab
- Binds to TNF trimers preventing cytokine from binding to its receptor
- Binds to membrane bound TNF α and neutralises its activity
- Reduces serum TNF α levels
Biologicals
Anti TNF α: Infliximab, adalimumab, golimumab Anti-IL23/IL12: Ustekinumab Anti-α4: Natalizumab Anti-α4β7: Vedolizumab JAK inhibitor: Tofacitinib Anti-IL6:Tocilizumab